We know that
K.E. = $\frac{{\mathrm{P}}^2}{2\mathrm{m}}$,  P: momentum,      m : mass
on increases momentum.  Let K.E. becomes KE¢ 
When momentum increases by 100% i.e :
P' = P + 100% of P = P + P = 2P
    % change in $\mathrm{KE}=\frac{{\mathrm{KE}}^{\mathrm{\prime }}-\mathrm{KE}}{\mathrm{KE}}=\frac{\frac{(2\mathrm{P}{)}^2}{2\mathrm{m}}-\frac{{\mathrm{P}}^2}{2\mathrm{m}}}{\left(\frac{{\mathrm{P}}^2}{2\mathrm{m}}\right)}$
$=\frac{(2\mathrm{P}{)}^2-{\mathrm{P}}^2}{{\mathrm{P}}^2}\times 100\mathrm{\%}=300\mathrm{\%}$